Abstract:

Guided by the carbon peaking and carbon neutrality goals, and propelled by the development of new type power systems, the significance of distribution networks as key energy infrastructure has been increasingly underscored. Amidst the burgeoning rise of distributed photovoltaics, electric vehicles, and novel energy storage technologies, distribution networks are transitioning from passive entities to active systems capable of bidirectional interaction, heralding the advent of active distribution networks with a critical mission. This research tackles the optimal power flow issue in three-phase unbalanced active distribution networks, incorporating inter-phase coupling relationships. By employing dimensionality lifting and rank relaxation, along with the Sylvester criterion, second-order cone constraints are established among voltages, currents, and powers. The branch flow model is expanded from a single time period to multiple periods. In line with the principles of the symmetrical component method and national standards, constraints on three-phase voltage unbalance are formulated. The study integrates active management and demand response strategies, targeting the minimization of active energy losses in distribution networks. A dynamic optimal power flow model for three-phase unbalanced active distribution networks is developed based on mixed-integer second-order cone programming, facilitating coordinated optimization of active and reactive power dispatch. The case study analysis demonstrates that the proposed method can effectively reduce the system's operational network losses, significantly improve the degree of three-phase voltage unbalance, and comply with the national standard's upper limit of 2%, thus providing valuable insights for precise modeling and simulation of three-phase unbalanced distribution networks.

Key words: active distribution network, three-phase unbalance, active management, demand response, mixed-integer second-order cone programming, dynamic optimal power flow